Map of the St. Louis area showing the position and track of the aircraft described in the post.

🇺🇸 N39728 - Boeing 737NG 724/W - United Airlines UAL1540/UA1540 (PHX-IAH-DCA) - 4.6 mi away @ 37850 ft, heading NE at 560 mph. Spotted 13x before! [04:30:58 PM CDT] #A49F89 #N39728 #B737 #UNITED #UAL1540 #UA1540 #ADSB #ADSBbot